Population centers in the U.S. and around the world face increasing challenges to provide safe water supplies, and will increasingly demand new technologies for reclamation and reuse of wastewater. Wastewater treatment is also desirable in many industries to prevent pollution of rivers, lakes, and groundwater.
Accordingly, the treatment of contaminated water will continue to be an important issue as science and techniques addressing water quality issues advance. The availability of technically and economically effective technologies for water treatment and reclamation is desirable. The presence of new contaminants of concern such as those identified by EPA's CCL 2 and effective methods for their control, therefore, is an important issue.
Many processes are currently available for bioremediation which have benefits and drawbacks. One such natural process is when water flows over stationary algae or periphyton. Water remediation by regularly harvested periphyton has been shown to be 50 to 1000 times higher than constructed wetland systems per unit area. Accordingly, remediation can occur when water flows over man-made or artificial stationary algae taking up macro nutrients (carbon, nitrogen and phosphorus) and micro nutrients, while discharging oxygen as high as three times saturation. Further, this high oxygen and hydroxyl environment can reduce organic sediments by 0.25 meters per year. In extended time experiments, periphyton increases pH due to carbon uptake to as high as 11. Filtration can occur through adsorption, absorption, physical trapping, and other more complex mechanisms.
Further studies of periphyton filtration are disclosed in U.S. Pat. Nos. 4,333,263; 5,131,820; 5,527,456; 5,573,669; 5,591,341; 5,846,423; and 5,985,147. Periphyton filters (PF) have found use in a variety of applications, for example, as filters in aquaria, natural periphyton are used to remove nutrients and other contaminants from polluted waters. However, such natural processes require large areas and consume vast resources and are impractical for large scale operation.
Other wastewater treatment techniques known in the art include the treatment of wastewater with ozone (triatomic oxygen or O3). Ozone is a naturally occurring gas created, for example, by corona discharge during lightning storms or by UV light from the sun. Ozone occurs in an upper atmospheric layer and is believed to be critical to temperature balance on Earth, while ozone in the lower atmosphere is commonly viewed as a pollutant. Ozone treatment is currently used for drinking and wastewater treatment as well as air filtration with doses taking into account health and safety factors. Examples of patents discussing the treatment of a sample with ozone include, among others, U.S. Pat. Nos. 7,014,767; 6,991,735; 6,394,329; 6,962,654; 6,921,476; 6,835,560; 6,780,331; and 6,726,885.
As well, it is known to use microbubbles to treat wastewater. Examples of the use of microbubbles to treat wastewater include generating microbubbles, coating them with a contaminant degenerative liquid, and passing the coated microbubbles through a wastewater stream. Other microbubble techniques include aeration of septic tanks by drawing atmospheric air into an expansion chamber and from there into agitated sludge to provide low pressure small microbubbles which have long residence times in the sludge material. Aeration devices which disperse microbubbles into a liquid and maintain transfer of gas to the liquid across a fiber membrane are also used where gas pressures are above the bubble point of the fiber membranes. A cloud of microbubbles is expelled into the liquid as it is forced to flow past the fibers. Although somewhat effective in decontamination, in large part due to increased contact surface areas, these approaches can be limited in their efficiencies, can require expensive equipment, and can be difficult to maintain.
Despite the above approaches and technologies, the need remains for methods and systems which can further increase treatment efficiencies and are safe, reliable and cost effective.